1. Field of the Invention
The present invention relates generally to magnetic detectors and, more particularly, is directed to a magnetic detector used to detect a position necessary for stopping vehicles of various kinds such as an elevator, unmanned or driverless train, car or the like at a predetermined position with high accuracy and smoothness and/or to lead an unmanned train and the like.
2. Description of the Prior Art
Generally, in order to position or stop a vehicle, various kinds of contactless switches are used to detect a stop position and a position before the stop position and on the basis of these detected positions, the vehicle is decelerated and then stopped at the predetermined stop position.
Another method for stopping the vehicle at the predetermined stop position, is proposed, which employs a multiplex magnetic detecting switch which detects a magnet plate located at the stop position of the vehicle and then produces an output changing stepwise before and after the stop point (see Japanese patent application No. 59-241738).
It is known to lead an unmanned train or car by an electromagnetic guidance system which uses an electric wire buried in the floor and a detecting coil mounted on the unmanned train or an optical system in which a white tape attached to the floor is detected by a photo-sensor. As other method, there is proposed a magnetic guide system in which a belt-shaped rubber magnet is attached on the floor and the position of this rubber magnet is detected by the multiplex magnetic detecting switch located on the unmanned or driverless train to thereby carry out the pilot control of the unmanned train (see also Japanese patent application No. 59-241738).
Since the above mentioned multiplex magnetic detecting switch produces a step-shaped control voltage, this switch has a problem in continuous servo control for the unmanned train. Further, in order to detect a range as wide as 300 mm, it is necessary to use several 10s magnetic detecting switches. Thus, a circuit arrangement of a magnetic detector becomes complicated in construction and becomes high in cost.
It is known to produce a non-contact type potentiometer by combining a magnetic generator and a magnetic detector. In the prior art system, the magnetic generator must be provided over the entire region in which the potentiometer is changed and also the magnitude of the magnetic flux from the magnetic generator has to be altered with the place in order to produce a linear output. Accordingly, the prior art non-contact type potentiometer is not suited as a magnetic detector used to lead an unmanned train or the like.